How Do Metal Ion Levels Change over Time in Hip Resurfacing Patients? A Cohort Study

Table 1

Profile of the cohorts of subject with metal-on-metal hip resurfacing at short (group  1), medium (group  2), and long term (group  3). Values are expressed as mean ± standard error (median) and minimum–maximum range.

Variable	Group 1	Group 2	Group 3
Gender
Males	8	10	15
Females	6	9	7
Age (years)	49 ± 3 (44) 26–75	53 ± 2 (55) 30–65	53 ± 2 (53) 26–73
Diagnosis
Osteoarthritis	7	14	16
Congenital hip dysplasia	5	3	3
Rheumatoid arthritis	1	—	1
Trauma	1		—
Necrosis	—	2	—
Epiphysiolysis	—	—	1
Coxitis	—	—	1
Follow-up (years)	2 ± 0.1 (2.0) 1.3–2.7	5 ± 0.05 (4.7) 4.6–5.2	9 ± 0.2 (8.5) 8.0–11.0
Body mass index	29 ± 2 (28) 23–40	27 ± 1 (27) 22–34	25 ± 1 (25) 17–32
Activity level (10-UCLA scale)	7.8 ± 0.5 (8.4) 5.9–10	6.9 ± 0.4 (6.0) 5.0–10.0	7.3 ± 0.4 (7.0) 3.0–10.0
Head diameter	48.7 ± 1.6 (46) 38–60	46.8 ± 3.2 (46) 38–54	48.9 ± 0.96 (50) 38–54
Acetabular component diameter	54.9 ± 1.2 (54) 46–60	54.4 ± 3.1 (58) 46–60	56.2 ± 0.93 (56) 46–62
Cup inclination angle	45 ± 2.2 (45) 30–59	46.0 ± 1.9 (45) 30–60	45 ± 1.2 (45) 32–58
Harris hip score	95 ± 1.8 (100) 83–100	95 ± 1.1 (96) 88–100	94.8 ± 1.6 (98) 69.7–100